1. Field of the Invention
This invention relates to bonding tools for bonding fine wires to make connections between electrodes and/or pads on semiconductor devices. More specifically the present invention relates to a method of making a composite or two-piece bonding tool.
2. Description of the Prior Art
Composite bonding tools are well known in the semiconductor art. U.S. Pat. No. 3,358,897, classified in class 228 subclass 41, shows a carbide bonding nib which has been press fitted into a magnetic steel holder which is adapted to be held or carried by a heated magnetic holder.
Micro Swiss Bonding Tool products, made by Kulicke and Soffa Industries, Inc. of Horsham, Pa. include numerous two piece or composite bonding tools, the most common of which include carbide nibs press fitted into steel holders and ceramic nibs press fitted into steel holders.
Further, numerous manufacturers throughout the world make and sell capillary bonding tools completely made of ceramic powder. There are two general methods of making all ceramic capillary bonding tools. The first is to pill press a preform shape blank approximately the shape of the desired tool and then sinter the blank. This method requires finishing all outside surfaces plus the bore and working face of the blank. The second method is similar to the first but includes injection moulding a ceramic powder into heated moulds to form a moulded ceramic blank which is set by heat and then sintered and finished.
Some prior art bonding tools, such as pure tungsten nibs are made from tungsten powder, by forming the blank on a mandrel. The mandrel is removed only after the tool blank or nib is sintered or partially sintered. Powder carbide nibs have been made by employing the aforementioned pill pressing techniques to make a blank or nib which is then sintered. Carbide tools employ binders.
It is well known that ceramic bonding tools do not require a binder, however, tungsten carbide and titanium carbide bonding tools employ a binder or binders to strengthen and hold the carbide particles together.
Synthetic ruby and sapphire are mono crystal aluminum oxide which have a Moh hardness of nine. Recently, bonding tools made completely of grown or drawn synthetic jewel material have been made commercially available. While all jewel bonding tools are very hard and have good working face wear characteristics, the long holder or shank portion is brittle like glass and requires expensive precise machining operations to form the feed hole and the bore as well as the outer shank and working face surfaces.
It would be desirable to make a composite bonding tool having a very tough material for a shank or holder portion and provide a synthetic ruby working face. It would be extremely desirable to make such a composite bonding tool by a series of precise steps which provided all the desirable features of prior art bonding tools and which cost less than synthetic jewel tools known heretofore.